• Fire Science and Engineering
• /
• v.27 no.2
• /
• pp.1-5
• /
• 2013

This paper studies on an arc fault interruption control circuit (AFICC) of fault voltage sensing type. The proposed voltage sensing type AFICC (VST_AFICC) is an electrical fire prevention apparatus that operates the existing circuit breaker with sensing the instantaneous voltage drop of line voltage when occurs electrical faults. The existing Earth Leakage Circuit Breaker (ELB), Molded_case Circuit Breaker (MCCB), and Residual Current Protective Devices (RCDs) used in low voltage distributing system don't have protective capability from electric arc faults to be a major factor of electrical fire. In this paper to improve such problems, a new VST_AFICC using the distortion of voltage waveform when occurs electrical faults is proposed to prevent electrical fire. There is characteristic that the control method of proposed apparatus is different from previous current sensing type. The proposed AFICC has merit that is manufactured by small size and light weight. The practicality of a new VST_AFICC is also verified through various operation analysis.

• Journal of Electrical Engineering and Technology
• /
• v.9 no.6
• /
• pp.2224-2236
• /
• 2014

The performance of an isolated high voltage full bridge converter is improved using a voltage doubler. In a conventional high voltage full bridge converter, the diode of the transformer secondary voltage undergoes a voltage spike due to the leakage inductance of the transformer and the resonance occurring with the parasitic capacitance of the diode. In addition, in the phase shift control, conduction loss largely increases from the freewheeling mode because of the circulating current. The efficiency of the converter is thus reduced. However, in the proposed converter, the high voltage dual converter consists of a voltage doubler because the circulating current of the converter is reduced to increase efficiency. On the other hand, in the proposed converter, an input current is distributed when using parallel input / serial output and the output voltage can be doubled. However, the voltages in the 2 serial DC links might be unbalanced due to line impedance, passive and active components impedance, and sensor error. Considering these problems, DC injection is performed due to the complementary operations of half bridge inverters as well as the disadvantage of the unbalance in the DC link. Therefore, the serial output of the converter needs to control the balance of the algorithm. In this paper, the performance of the conventional converter is improved and a balance control algorithm is proposed for the proposed converter. Also, the system of the 1.5[kW] PCS is verified through an experiment examining the operation and stability.

• Journal of Korea Society of Industrial Information Systems
• /
• v.23 no.1
• /
• pp.43-52
• /
• 2018

This paper presents the performance of a Phase Shift Full Bridge (PSFB) converter with inductive load and a new current control scheme to improve dynamic response of output current with various inductive loads. Enhanced dynamic model is used which includes leakage inductance and inductive load. Effect of changing of inductive load was analyzed in detail. Proposed current control scheme is designed based on phase margin specifications. As a result, the proposed current control scheme helps to improve the dynamic response in comparison with the existing current control scheme. The performance of the designed controller is verified by a 500 A PSFB converter. The results will be utilized for high current applications with high inductive load such as superconducting devices.

• Journal of Korean Society for Atmospheric Environment
• /
• v.21 no.6
• /
• pp.573-583
• /
• 2005

Fugitive dust, which is emitted in the ambient air without first passing through a stack or duct designed to control flow, is frequently generated by means of wind erosion from storage yards at Pohang Steel Wokrs. The size distribution of fugitive dust is mostly in the range of coarse particulate which is deposited as soon as emitted and less harm to human health; however $20\%$ of fugitive dust contains PM 10 known as one of most harmful airborne pollutant. Consequently, effective control and reduction of fugitive dust is strongly requested by the local society, but it is not easy so far because the generation and dispersion of fugitive dust highly depends on meteorological conditions, and it being occurred for irregularity. This research presented a fugitive dust control system for each meteorological condition by providing statistical prediction data obtained from a statistical analysis on the probability of generating the threshold velocity at which the fugitive dust begins to occur, and the frequency occurring by season and by time of the wind direction that can generate atmospheric pollution when the dispersed dust spreads to adjacent residential areas. The research also built a fugitive dust detection system which monitors the weather conditions surrounding storage yards and the changes in air quality on a real-time basis and issues a warning message by identifying a situation where the fugitive dust disperses outside the site boundary line so that appropriate measures can be taken on a timely basis. Furthermore, in respect to the spraying of water to prevent the generation of fugitive dust from the storage piles at the storage yard, an advanced statistical meteorological analysis on the weather conditions in Pohang area and a case study of fugitive dust dispersion toward outside of working field during $2002\∼2003$ were carried out in order to decide an optimal water-spraying time and the number of spraying that can prevent the origin of fugitive dust emission. The results of this research are expected to create extremely significant effects in improving surrounding environment through actual reduction of the fugitive dust produced from the storage yard of Pohang Steel Works by providing a high-tech warning system capable of constantly monitoring the leakage of fugitive dust and water-spray guidance that can maximize the water-spraying effects.

• Fire Science and Engineering
• /
• v.33 no.3
• /
• pp.74-83
• /
• 2019

In the U.S., the pressurization of elevator shaft was developed in 1972 to allow vulnerable people, such as the elderly and weak who could not use escape stairs in case of fire, to evacuate. It is an advantage in terms of space saving by not using vertical ducts. This study drew the problem of the pressurization of elevator shaft based on the existing domestic patents and proposed improvements. The smoke control volume calculation method is proposed by using vertical modeling. Leakage gaps in elevator doors need to be reviewed through experimental data or actual data. The evacuation floor was divided, the openings in the elevator machine room were automatically closed to the fire signal and the relief damper was installed to improve the performance. The improved method functions as the smoke control damper supplying the air flow rather than maintaining the differential pressure. To increase reliability of the research results, the procedure was performed to verify by using Contam.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.24 no.4
• /
• pp.172-179
• /
• 1988

A cartridge type hydraulic logic valve consists of simple two port valve whose poppet is closed or opened by means of pressure signal of a pilot line. Accordingly, the logic valve can be used not only for direction, flow and pressure control purpose but also for versatile function valve which enables all above mentioned functions. In addition, the valve has little internal leakage and pressure loss, superior response characteristics and easiness in making small block type valve. The above mentioned good performances being recognized recently, the logic valve has been used widely in the large scale hydraulic system such as a hydraulic press system, for the performance requirements of high speed operation and precise control characteristics. However, there are scarce reports until now, except for a few ones from Aachen Institute of Technology in West Germany, so it is necessary to be studied on development and investigation for practical application. This paper showed that the static and dynamic characteristics of a logic valve when the logic valve is used for directional control, to investigate the relations between the valve operating characteristics and the valve design conditions. From the above mentioned procedure, it was ascertained that the valve operation characteristics obtained by numerical analysis showed good agreements with experimental results. The representative results obtained are as follows; 1. During the valve is closing, the poppet velocity is almost constant in the logic valve. 2. The pilot pressure P sub(3) and the resistance R in the pilot line have much influences on the valve operation time. 3. Spring strength have not such a severe influence on the valve operating time. 4. The operation characteristics of the logic valve can be estimated with good accuracy comparatively by numerical analysis with the equations describing poppet motion.

• Convergence Security Journal
• /
• v.17 no.5
• /
• pp.35-40
• /
• 2017

The control system can have such threats as information leakage and falsification through various routes due to communications network fusion with public network. As the issues about security and the infringe cases by new attack methods are diversified recently, with the security system that makes information data database by simply blocking and checking it is difficult to cope with new types of threats. It is also difficult to respond security threats by insiders who have security access authority with the existing security equipment. To respond the threats by insiders, it is necessary to collect and analyze Event Log occurring in the internal system realtime. Therefore, this study could find out whether there is correlation of the elements among Event Logs through correlation analysis based on Event Logs that occur real time in the control system, and based on the analysis result, the study is expected to contribute to studies in this field.

• Journal of the Korea Society of Computer and Information
• /
• v.28 no.11
• /
• pp.73-80
• /
• 2023

In this paper, a technology to protect important information from access in order to revitalize the cloud service market. A technology is proposed to solve the risk of leakage of important confidential and personal information stored in cloud systems, which is one of the various obstacles to the cloud service market. To protect important information, access control rights to cloud resources are granted to cloud service providers and general users. The system administrator has superuser authority to maintain and manage the system. Client computing services are managed by an external cloud service provider, and information is also stored in an external system. To protect important in-house information within the company, all users, it was designed to provide access authority with users including cloud service providers, only after they are authenticated. It is expected that the confidentiality of cloud computing resources and service reliability achieved through the proposed access control technology will contribute to revitalizing the cloud service market.

• Journal of Chest Surgery
• /
• v.24 no.2
• /
• pp.123-134
• /
• 1991

Twenty eight patients had undergone repair of an isolated complete atrioventricular septal defect between April 1986 and September 1990 in Seoul National University Children`s Hospital. The group comprised 13 male and 15 female patients. They ranged in age from 2 months to 8 years[mean 18.6months] and in weight from 3. 4kg to 23kg[mean 9.0$\pm$4.6kg]. They were analysed as Rastelli type A in 17 patients, Rastelli type B in 2 patients, and Rastelli type C in 9 patients. Seven patients had concomitant Down`s syndrome. All patients had large left-to-right shunt[mean pulmonary to systemic flow ratio 3.5 $\pm$2.2 ranging from 0.68 to 10.0] and high pulmonary systolic pressure[mean 74$\pm$18.8mmHg, ranging from 35 to 110]. In 11 patients, one patch technique was used to close the atrial and ventricular septal defect and 16 patients were undergone by two patch technique. We urgently managed only one patient by pulmonary artery banding whose anatomy was Rastelli type C and severe mitral regurgitation was identified. Postoperative complete A - V block was noted in 3 patients, two of whom were dead in operating room due to combined LVOTO and myocardial failure, and one patient with Rastelli type C was undergone by VVI type permanent pacemaker insertion 1wk later after two patch technique, but we had to manage him by modified Konno operation and total correction due to LVOTO and VSD leakage and severe mitral regurgitation 3 years later. Another two reoperation cases due to severe mitral regurgitation after two patch technique were undergone, one of whom we managed by mitral annuloplasty 3 months later but aggravated mitral regurgitation made us to control him by MVR 3 months later. Another one case of VSD leakage and tricuspid regurgitation was managed by total correction but she died of respiratory insufficiency 14 days later. We experienced pulmonary hypertensive crisis in 3 patients, who were dead in two cases comparing with one control case. So operative mortality is 9/27[33.6%], in one patch group of 3/11[29.2%] comparing with two patch group of 6/16[37.5%]. In summary, causes of death were pump weaning failure, myocardial failure and low cardiac output syndrome and pulmonary hypertensive crisis, resp. failure, complete AV block. Mean follow up period is 15.8$\pm$10.7 months[ranging from 3months to 37 months]

• Journal of radiological science and technology
• /
• v.32 no.1
• /
• pp.1-15
• /
• 2009

Newly published IEC 60601-1-3 ; 2008 2nd Edition has two important meanings. First, Radiation Quality and Dose should make sure for safety of patient and staff in manufacturing diagnostic X-ray equipment. Second, it should be minimized of Leakage Radiation, Residual Radiation, and Stray Radiation. The requirement to make enactment or revision of national standard for diagnostic X-ray Equipment is as follows : 1. It should be adjusted the new standard to the recent IEC Publication under the consideration of the Korea medical circumstances. 2. For focus to the Radiation Safety, IEC 60601-1-3 (General requirements for radiation protection in diagnostic X-ray equipment) could be applied to the new regulation. It should be compact sentence. 3. A sudden Notification change should not be desired. It needs a enough time to make easy the circumstances.